Recording hygrothermographs and dataloggers

Tom Dixon <tom.dixon [at] ngv__vic__gov__au> writes

>I would be grateful to hear from the list regarding positive and
>negative experiences of replacing recording hygrothermographs used
>for simultaneous monitoring of several large gallery spaces on a
>long term and continuous basis with newer technology.

They each have their place.  I have 2 recording hygrothermographs in
the lab (one with one hair bundle, another with 8 hair bundles), and
three data loggers.  Two are for downloading only; the third has an
LCD panel which allows the operator to push a button for a current
read-out of temperature or%RH, and collects data which can be
downloaded.

I like to mail the data loggers a couple of weeks in advance of a
visit to a museum or library, and suggest where it should be placed
and moved to every 2-3 days for a variety of readings which I can
download on my laptop computer upon arrival.

In 'sealed' exhibit cases in a museum I think that data logger
probes wired to a central computer are appropriate.  The software
can be set to alert a responsible person if certain pre-set limits
are exceeded.

When I assisted in the design of a large 'sealed' exhibit case I
made certain there there was a plugged hole in the background.
Periodically, I can remove a panel in the plinth, replace the plug
with a probe from the datalogger (a neoprene gasket keeps things
tight) and determine the state of the environment inside the case.

But for the general public visiting a museum, I believe that
recording hygrothermographs, visible but discreet, are an important
assurance that professional attention is being paid to the
collections and their environment.

Changing the charts is important (as you report) but when the weekly
charts remain unchanged for a few weeks (as I have witnessed), the
effect is muted.

Jack C. Thompson
Thompson Conservation Lab.
7549 N. Fenwick
Portland, OR  97217
503-735-3942  (voice/fax)


                                  ***
                  Conservation DistList Instance 14:46
               Distributed: Wednesday, February 21, 2001
                       Message Id: cdl-14-46-004
                                  ***